s, the fire is all
round the chamber, but not in it, the fumes of the sulphur being
destructive of the enamel if they are allowed to come into contact
with it. So intense is the heat, however, that a muffle lasts only
about nine days, and at the end of that time has to be renewed.

[Illustration: FIRING THE LETTERS]

After the enamel is fused on to the copper, the disk is taken out and
placed on a side slab, where it is allowed to cool.

This process is repeated on the front side of the letter, when all
that remains to complete it is

THE FILING.

[Illustration: FILING THE LETTERS AFTER ENAMELING.]

This is done by girls, who, with very fine files, rub off the edges
and any protuberances which may be there. Every letter is subject to
this operation, and all are turned out smooth and well finished.

Sometimes the letters are colored or further defined by the addition
of a line, but the essentials are as we have already described.

[Illustration: MIXING THE ENAMEL]

BRUSHING OUT.

There are, however, one or two other operations of interest which we
may notice. The company do not confine their exertions to the making
of letters, various collateral developments having taken place which
fill an important part in this scheme of work.

Of these, small tablets, containing advertisements or notices, such as
we see in railway carriages, "Push after raising window," or "Close
this door after you," or some legend pertaining to Brown's Soap or
Robinson's Washing Powder. These are done by different processes, the
transfer process, as used in the potteries, being employed, but the
one most largely used is that of "brushing out," which is done by
plates.

Let us suppose that the tablet shows white letters on a dark ground,
the _modus operandi_ is as follows:

The tablet has been enameled, as already described, and is white. The
operator now takes a dark enamel and spreads it evenly over the entire
surface of the tablet. He, or she, now takes a stencil plate, of
tinfoil, out of which the ground is cut, leaving the letter in the
center.

This is carefully placed over the tablet and held tight with the left
hand, while with the right hand he holds a fine brush, which he uses
with a quick, sharp movement over the surface. This action readily
removes the unfired color from the hard, glassy surface underneath,
and leaves a white letter. This is fired, and is then complete.

Sometimes two and, it may be, three plates a